1. Field of the Invention
The present invention relates to a method and device for controlling the temperature of an object using heat transfer fluid.
2. Description of the Related Art
Temperature-controlled heat transfer fluid is used in a processing chamber for processing a semiconductor wafer in a plasma atmosphere in order to control the temperature of a table on which the semiconductor wafer is placed (to be referred to hereafter as “susceptor”). The heat transfer fluid is brought to an appropriate temperature using a temperature adjusting device (for example a chiller for cooling high-temperature heat transfer fluid returned from a chamber) which is disposed in a location removed from the chamber, and then transferred from the device to the chamber and circulated around the susceptor. The heat transfer fluid is then removed from the chamber and returned to the temperature adjusting device.
As is illustrated in FIG. 1, this type of temperature adjusting device conventionally measures the temperature T1 of heat transfer fluid newly discharged from the device and controls the amount of heating or cooling to be performed on the heat transfer fluid such that the measured discharge temperature T1 thereof reaches a set temperature SV.
According to this conventional method of controlling the discharge temperature of heat transfer fluid to a set temperature, it is difficult to suppress a large rise in the temperature of the susceptor when a thermal load (disturbance) is applied to the susceptor at the beginning of plasma processing in the processing chamber. To explain in more general terms, when controlling the discharge temperature of heat transfer fluid, it is difficult to sufficiently suppress temperature variation in the object of temperature control when a thermal load is applied to this object.
Also according to such discharge temperature control, the temperature of an object of temperature control such as a susceptor may vary greatly due to the effects of heat loss or heat resistance, or due to wasted time, delays and the like, in the piping or chambers existing on the outside of the temperature controlling device.
A well-known method also exists in which a control operation is performed such that the temperature of the object of temperature control itself is detected and controlled to a set temperature. However, since the temperature of the object of temperature control is controlled indirectly via the heat transfer fluid, it is difficult to reduce temperature variation in the object of temperature control when the control operation is performed based only on the temperature of the object of temperature control itself.